System comprising organic or metallo-organic energy and/or charge variable moieties

ABSTRACT

The invention relates to a system for use in an electric or optical device comprising at least two organic or metallo-organic energy and/or charge variable moieties having conjugated unsaturated bonds, wherein at least one moiety has an energy state different from another of said moieties, characterized in that the system is a H-donor-Hacceptor system comprising at least one H-donor molecule having at least two hydrogen bonding clusters, each cluster comprising at least two groups having formed a hydrogen bond, and at least two H-acceptor molecules, each having at least one hydrogen bonding cluster, each cluster comprising at least two groups having formed a hydrogen bond with the groups of the H-donor molecule, at least one of the H-donor and H-acceptor molecules 10 further comprising one or more of the organic or metallo-organic energy and/or charge variable moieties.

System comprising organic or metallo-organic energy and/or chargevariable moieties The invention relates to a system comprising at leasttwo organic or metallo-organic energy and/or charge variable moietieshaving conjugated unsaturated bonds, wherein at least one moiety has anenergy state different from another of said moieties for use in anelectric or optical device and to an electronic device comprising saidsystem.

Such systems and electronic devices comprising said systems are known inthe art as such. For example, electroluminescent devices are known whichhave an electroluminescent layer, which includes a semi-conductingpolymer, which is mixed with a luminescent dye. In such a device lightemission from the dye is achieved by charge injection from electrodes(holes from the anode, electrons from the anode) into theelectroluminescent layer producing hole and electron states in thesemi-conducting polymer which states are then transferred within thepolymer. Hole and electron states meet on the polymer to form an excitedstate. The excited state on the polymer is then transferred to bring theluminescent dye into an excited state which state may then revert backto the ground state by emission of a photon of light. In another knownexample of such a system a first and a second moiety are dyes having anexcited state of different energy leading to a different absorption andemission color.

A known type of such material system is one wherein the first and secondmoieties are incorporated in separate compounds, which are mixedtogether to form the material system. A drawback of such type of systemis that if such system is used in the form of a thin film of anelectronic device the first and second moieties have a tendency tomigrate relative to another during the service life of the device, onoccasion, even to the extent that phase-separation or aggregationoccurs. Such migration changes the properties of the electronic deviceduring operational lifetime, which is undesirable. When used inelectronic devices such systems may be used for obtaining layers forfull-color displays. These require the availability of pure red, green,and blue emitters. The different emission colors are realized byapplication of a blue luminescent material, doped with suitable greenand red emitting luminophores. The use of such single molecule dopants,usually applied as solid solution in an electroluminescent material, iswell known in the art, as is the problem of migration of the lowmolecular weight material in the polymer. In lighting systems theproblem is in the realization of pure white emitting layers. Also insuch layers combinations of different emitters are used.

Another known type of material system is one first and second moietyincorporated in a polymer as distinct structural units. Being covalentlylinked together, the problem of migration is solved but for eachcombination of first and second organic moiety a separate syntheticeffort is required which is laborious and not versatile. Also, synthesisand thin film formation of such integrated systems is generallydifficult to do in a controlled manner, since the thin films generallyhave a relative large number of defects such as impurities. This isparticularly true when the integrated system is a polymer. In view ofits large molecular weight a polymer is difficult to purify and analyze.Also, with polymers, morphology is an important parameter for deviceperformance yet is difficult to control. Lack of control and arelatively high defect density obviously has a negative impact on deviceperformance and reproducibility of device manufacture of electronicdevices comprising thin films formed of such integrated systems.

It is an object of the invention to take away or at least mitigate theabove-mentioned drawbacks. Specifically, an object is to provide amaterial system which is suitable for use in an electric or optical,electronic and electro-optical in particular, device, which can besynthesized and formed into thin films in a controlled and versatilemanner and has a significantly lower level of defects than conventionalintegrated material systems. Like systems having the first and secondmoieties in separate compounds, it should be easy to form newcombinations. However, unlike systems having the separate first andsecond moiety, migration during operational lifetime of a devicecomprising such system should be substantially absent.

These and other objects are achieved using a system as mentioned in theopening paragraph, which in accordance with the invention, ischaracterized the system is a H-donor-H-acceptor system comprising atleast one H-donor molecule having at least two hydrogen bondingclusters, each cluster comprising at least two groups having formed ahydrogen bond, and at least two H-acceptor molecules, each having atleast one hydrogen bonding cluster, each cluster comprising at least twogroups having formed a hydrogen bond with the groups of the H-donormolecule, at least one of the H-donor and H-acceptor molecules furthercomprising one or more of the organic or metallo-organic energy and/orcharge variable moieties.

It has now been found that novel systems comprising charge and/or energyvariable moieties having states of different energy bound together byhydrogen bonds provide an extremely versatile way to compose electricalor optical, in particular electronic and electro-optical andelectroluminescent, materials. The resulting material forms a stablelayer, which is held together with hydrogen bonds and has excellentmechanical properties. It was found that supramolecular systems asdescribed in A. El-ghayoury, et al., Angew. Chem.. 2001-40/19, p.3660-3663, and in A. Schenning, et al., J. Am. Chem. Soc. 2001, 123, p.409-416 for use in other applications than the instantly claimedelectric or optical devices with different energy and/or charge variablemoieties, could form the basis for suitable materials for use in theinstantly claimed electronic devices. These references describe thesynthesis and organization of chiral π-conjugated oligo(p-phenylenevinylene) (OPV) molecules, such as MOPV and 13OPV. Both MOPV and BOPVcontain an organic energy variable moiety rendering these moleculessuitable for use in electronic devices, such as LEDs (light emittingdiodes), solar cells, and FETs (field effect transistors). These systemsare self-assembled, and depending on the condition used the bifunctionalBOPV may form a random coil polymer of frustrated stacks, but theassemblies disclosed therein are do not have at least two organic ormetallo-organic energy and/or charge variable moieties having conjugatedunsaturated bonds, wherein at least one moiety has an energy statedifferent from another of said moieties and accordingly do not have theproblem of migration.

The present inventors have now found that such systems could very wellbe used for the presently claimed type of electronic devices when suchsystems were so changed that at least one moiety has a different energystate than the other moieties. The inventors farther realized that suchsystem could provide a versatile system not having the hereinabovementioned migration problems and being perfectly suitable for theabove-mentioned types of electronic devices.

The terms “H-donor” and “H-acceptor” only relate to molecules thatprovide the hydrogen atom for bonding (H-donor) or accept the hydrogenatom for bonding (H-acceptor). These terms are only relative, since thesame H-donor molecule can also be an H-acceptor molecule and vice versa.It is also possible that one groups acts as H-donor hydrogen, whereasanother group in the same molecule acts as H-acceptor hydrogen.

The term “energy and/or charge variable” as used for the organic ormetallo-organic moieties having conjugated unsaturated bonds means thatsuch moieties are able to change their energy state by accepting ordonating electrons, holes or photons.

Since the starting material is a small low molecular weight) molecule,which can be prepared and purified with synthetic methods typical formolecular synthetic organic chemistry, extremely pure andwell-controlled electroluminescent materials can be prepared. To obtaina sufficient thermal and mechanical stability, the H-bonding structuresshould be constructed so that multiple bonds are supported in ageometric fashion that affords the formation of several H-bondssimultaneously. For example, one may use materials built up throughquadruple hydrogen-bonded self-complementary ureido-pyrimidone units.Mixed molecules, equipped to sustain multiple H-bonds, for generation ofwhite light (lighting) and for generation of pure emission (red, green,and blue) for full-color displays can be easily obtained, by mixing ofthe appropriate emitters. The charge transfer properties of the layer orlayers comprising the active stack in a thin-film electronic device maybe optimized by application of suitable energy and/or charge transfermoieties.

Hydrogen bonds are well known and can be obtained by O-, N-, S-, andP-containing units. The strongest hydrogen bonds are usually found for Nand O units, and for that reason the preferred hydrogen bond is anN—H—N, O—H—O, or N—H—O bond.

To give highly ordered structures, e.g. “tapered” systems of monomersthe H-donor and H-acceptor molecules are organized. The approach is mostsuitable for systems of similar molecules, wherein the H-acceptormolecule hydrogen bonding groups are complementary to the hydrogenbonding groups of the H-acceptor molecule.

The organic energy and/or charge variable moiety is a group that allowsenergy transfer, such as exciton, hole, or electron (charge) transfer,or a combination of functionalities. Preferred organic energy variablemoieties are semi-conductors and/or (luminescent) dyes.

The system can be a supramolecular H-bonded polymeric assembly, which isan assembly of distinct molecules that are linked together by H-bonds.More particularly, in order to obtain a stable assembly, the moleculesforming the assembly each have one or more hydrogen bonding clusters. Ahydrogen bonding cluster is a structural unit which comprises at leasttwo, preferably three or four, hydrogen bonding groups which each haveformed a hydrogen bond with one of the hydrogen bonding groups of ahydrogen bonding cluster of another molecule of the assembly. Asupramolecular H-bonded assembly which is polymeric is obtained if theassembly comprises a plurality of molecules which each have at least twohydrogen bonding clusters, and which are otherwise structurally the sameor different, wherein the molecules are connected to each other via theH-bond clusters to form a chain or chains of such molecules within theassembly.

The molecules comprising the H-bond clusters are compared to polymersrelatively small and are consequently easy to obtain in high purity anddo not have a distribution in molecular weight. Since the H-bondedassembly is assembled in situ., that is during orjust prior to thin filmformation, each new combination of H-donor and H-acceptor does notrequire a separate synthetic effort. On the other hand, since the bondbetween two hydrogen bonding clusters is strong, the strength mayapproach or even be the same as that of a covalent bond, migrationtypical fbr assemblies having separate guests and hosts is effectivelyprevented. Efficient energy transfer requires the donor state to be ofequal or higher energy than the acceptor state, close proximity of themoieties between transfer is to take place and proper mutual orientationof such moieties. Since H-bonds are highly directional and assemblyproceeds in an orderly manner the supramolecular assembly in accordancewith the invention is very well suited to satisfy these requirements.

A supramolecular H-bonded polymeric assembly is known as such in theform of polymeric assemblies of bifunctional ureidopimidone derivatesfrom Brunsveld, et al, Chem. Rev., 101 (12), p. 4071-4097 and from R. P.Sijbesma and E. W. Meijer, Current Opinion in Colloid & InterfaceScience 1999:4, p. 24-32. These systems are suggested to be useful incatalysis and material science, and are not suitable for use inelectronic devices since they do not contain groups that are able totransfer energy.

By way of example, the principle of the invention is illustrated by thefollowing schematic representation. The rectangles represent an organicenergy and/or charge variable moiety; the triangles represent ahydrogen-bonding cluster comprising at least two H-bonding groups. Inthe scheme a bifunctional molecule is depicted comprising two H-bondingclusters and two semiconductor moieties. A more specific example of sucha molecule is given (BOPV). Molecules with more or less hydrogen bondingclusters and energy and/or charge variable moieties can also be used.This molecule represents the H-donor molecule, which together with anH-acceptor molecule forms the system. The hydrogen bonding groups in theclusters of the H-donor and H-acceptor molecules are complementary andform a hydrogen bond to each other.

The larger rectangles represent energy and/or charge variable moietieswith a lower energy state. Such energy and/or charge variable moiety maybe a dye. The triangles represent hydrogen-bonding clusters. This systemis particularly useful when applied in LEDs. In a energy variable moietyof lower energy state the LUMO is of a lower energy state, the HOMO isof a higher energy state, or the distance between the LUMO and HOMOlevels is smaller than in the other energy variable moieties. When, forinstance, using OPVs of different conjugation length as building blocks,mixed columns arise. Upon excitation the short H-donor OPVs funnel theirenergy to the longer OPVs of lower energy state, which act as energytraps inside the stack.

It is required that the energy and/or charge variable moieties compriseconjugated unsaturated bonds, such as aromatic moieties, particularlybenzene, or homonuclear or heteronuclear aromatic groups, and aliphaticpolyene systems, such as dienes, trienes, and also polyene systemscomprising triple unsaturated bonds.

Preferably, the H-donor-H-acceptor system comprises at least 2 of theH-donor molecules and at least 3, preferably at least 4, of theH-acceptor molecule. Examples of systems according to the invention are,for instance, given by the following schematic representations.

wherein evm is the energy and/or charge variable moiety, for instance asemi-conductive moiety, and c is the hydrogen bonding cluster. Forsimplicity only one cluster is depicted, but at least one of the H-donoror H-acceptor molecules comprise at least two of such clusters.

It is clear that the H-donor and H-acceptor molecules can be used asbuilding blocks for obtaining many various systems, such as chains,monoclusters, multiclusters, networks, and the like, and combinationsthereof.

The systems in accordance with the invention are supramolecular H-bondedpolymers. Such H-bonded polymers are analogous to and accordingly arereadily available in the same variety as conventional polymer in whichrepeating units are covalently linked together to form the polymer, theH-acceptor and H-donor molecules of the H-polymer being the analogue ofthe repeating unit. Consequently, H-bonded polymers may be provided inthe form of co-polymers, for example of the AABB or the AB repeatingunit type or as a cross-linked systems if three or more H-bondingclusters are used in a H-donor or acceptor optionally in combinationdonor/acceptor having two clusters. Side-chain and main-chain H-polymersare also easily obtained. The charge and/or energy moieties may beincluded anywhere within the H-bond polymer, for example spliced betweentwo H-bonding clusters of a molecule or as a pendant group by means of amolecule having only a single H-bonding cluster.

In another preferred embodiment the invention relates to aH-donor-H-acceptor system comprising at least one H-donor moleculehaving at least two hydrogen bonding clusters, each cluster comprisingat least two groups having formed a hydrogen bond, and at least twoH-acceptor molecules, each having at least one hydrogen bonding cluster,each cluster comprising at least two groups having formed a hydrogenbond with the groups of the H-donor molecule, at least one of theH-donor and H-acceptor molecules further comprising at least an organicor metallo-organic energy and/or charge variable moiety havingconjugated unsaturated bonds, wherein at least one of the H-acceptor andH-donor has formed a complex or is bonded to a backbone having aplurality of hydrogen bonding clusters.

Examples of systems according to this embodiment comprise systemscovalently or ionogenically bonded to a backbone having a plurality ofhydrogen bonding clusters such as polymers or oligomers. Such bonding ofpoly- and oligomers can also be in the form of a complex with theH-donor, H-acceptor, or both. Any suitable poly- and oligomers can beused, such as polyethers, polyamides, polyacrylates, polyurethanes,oligomers thereof, mixed oligo- and polymers, and the like. Suchpoly-and oligomers may be linear, branched or hyperbranched. Aparticularly suitable form is a poly-or oligomer being complexed to theH-acceptor, H-donor, or both. A few non-limitative embodiments of theinvention are, for instance, given by the following schematicrepresentations.

wherein evm is the energy and/or charge variable moiety, for instance asemi-conductive moiety, and c is the hydrogen bonding cluster. P1 and P2are a polymer or oligomer, of which at least one is present. Thepolymers can be bonded to the energy transfer and/or charge moiety ordirectly to the hydrogen-bonding cluster. As above, at least one of theenergy transfer and/or charge moieties may have a lower energy statethan the other organic energy variable moieties, but when using thepolymeric or oligomeric additive this is no longer prerequisite.

In a specific embodiment the polymer is a hyperbranched polymer, such asa dendrimeric compound, which can form a complex with theH-donor-H-acceptor molecule of the invention, for instance via a bindingmotive as was described in Baars, et al., Angew. Chem. Int. Ed. 2000,(39), p 4262-4265. In the case of the supramolecular dendriticH-acceptor-H-donor system smooth homogeneous thin films could beobtained by spin coating. The dendritic H-donor-H-acceptor complexesshowed a significantly higher emission upon binding then that of theindividual molecules due to the three-dimensional orientation of theH-donor molecules. In the solid state this enhancement in luminescencewas a factor of ten. The complex may be represented as in the followingfigure (wherein the symbol above the reaction arrow represents theH-donor or H-acceptor).

For easy manufacturing of electronic devices, such as aelectroluminescent device (particularly LED's), field-effect transistor,sensor or photovoltaic device, it is advantageous that the H-donor andH-acceptor molecules dissolve in a solvent, to obtain a solution withsuitable viscosity to (spin-)coat or print it onto a substrate.

The invention is further illustrated by the following non-limitativeexamples.

EXAMPLE 1

1,6-Bis{2-amino-4-hexadiylureido-6-[(E,E)-4-(4-{3,4,5-trisdodecyl-oxystyryl}-2,5-bis[(S)-2-methylbutoxy]styryl)phenyl]-s-triazine}(BOPV-3) and4-amino-2-butylureido-6-[(E,E,E,E)-4-{4-[4-(4-{3,4,5-trisdodecyloxystyryl}-2,5-bis[(S)-2-methylbutoxy]styryl)-2,5-bis[(S)-2-methylbutoxy]styryl]-2,5-bis[(S)-2-methylbutoxy]styryl}phenyl]-s-triazine(MOPV-5) were prepared according to the method of A. Schenning, et al.,J. Am. Chem. Soc., 2001, 123, p.409-416.

The hydrogen-bonded systems have been applied in LEDs in order toinvestigate their suitability as active medium in an electroluminescentdevice.

The OLED was prepared using glass covered with indiumtinoxide (ITO) astransparent conductive substrate. A thin (135 nm) layer of theconductive polymer poly(ethylenedioxythiophene) (PEDOT), applied byspin-coating from an aqueous suspension of PEDOT with polystyrenesulfonic acid, was used as hole transporter. On top of the PEDOT layer,a very thin (about 70 nm) layer of BOPV-3 and BOPV-5 (10%) was appliedby spin-coating. Finally, the cathode was applied by evaporation of 5 nmBa (rate 0.1 nm/s) and 70 nm A1 (rate 1 nm/s).

The OLED was characterized by investigation of the current vs. voltageand luminance vs. voltage curves. The OLED has a turn-on voltage ofapproximately 2.5 V and shows a clear orange electroluminescence. Thedevice properties of the BOPV-3 and BOPV-5 mixture prove thathydrogen-bonded units, e.g. urideo-triazine units, and that the conceptof mixed systems, can be applied in OLEDs.

EXAMPLE 2

(Dendritic Structure)

Synthesis of(E,E,E)-4-[4-{3,4,5-tridodecyloxystyryl)-2,5-bis[(S)-2-methylbutoxy]styryl}-2,5-bis[(S)-2-methylbutoxy]styryl}phenyl]ureidoacetic acid methyl ester.

To a stirred solution of(E,E,E)-4-[4-{3,4,5-tridodecyloxystyryl)-2,5-bis[(S)-2-methylbutoxy]styryl}-2,5-bis[(S)-2-methylbutoxy]styryl]phenyl isocyanate (see Peeters, E; van Hal, P. A.; Meskers, S. C. J.;Janssen, R. A. J.; Meijer, E. W., Chem. Eur. J. 2002, 8, 4470, andSyamakumari, A; Schenning, A. P. H. J.; Meijer, E. W., Chem. Eur. J.2002, 8, 3353) in dry dichloromethane (3 ml) was added Et₃N (0.4 ml) andglycine methyl ester hydrochloride (53 mg, 1.1 eq). The mixture wasstirred overnight at room temperature. The product was washed withdiluted aqueous hydrochloride solution (0.2 M) and a saturated solutionof NaCl. The organic layer was dried over Na₂SO₄, filtrated andconcentrated in vacuo to yield 0.4 g of(E,E,E)-4-[4-{3,4,5-tridodecyloxystyryl)-2,5-bis[(S)-2-methylbutoxy]styryl}-2,5-bis[(S)-2-methylbutoxy]styryl}phenyl]ureidoacetic acid methyl ester) (80% yield) as a yellow solid. 7 eq ofLiOH.H₂O were added to a solution of the above methyl ester (1 eq) inThBF (tetrahydrofuran). The solution was stirred overnight (15 h) andthe acid was precipitated by acidification with HCl 1M (pH 2). Theresulting solid was filtered off, dried under high vacuum and thenwashed with hexane at room temperature giving OPV-5):(E,E,E)-4-[4-{3,4,5-tridodecyloxystyryl)-2,5-bis[(S)-2-methylbutoxy]styryl}-2,5-bis[(S)-2-methylbutoxy]-styryl]ureidoacetic acid (Mp: 122° C.).

Complexation of OPV-5 with the fifth generation polypropylene imine)dendrimer functionalized with urea adamantyl units at the periphery wassimply achieved by addition of 32 eq of OPV-5 to a solution of thedendrimer.

1. A system for use in an electric or optical device comprising at leasttwo organic or metallo-organic energy and/or charge variable moietieshaving conjugated unsaturated bonds, wherein at least one moiety has anenergy state different from another of said moieties, characterized inthat the system is a H-donor-H-acceptor system comprising at least oneH-donor molecule having at least two hydrogen bonding clusters, eachcluster comprising at least two groups having formed a hydrogen bond,and at least two H-acceptor molecules, each having at least one hydrogenbonding cluster, each cluster comprising at least two groups havingformed a hydrogen bond with the groups of the H-donor molecule, at leastone of the H-donor and H-acceptor molecules further comprising one ormore of the organic or metallo-organic energy and/or charge variablemoieties.
 2. The system of claim 1 wherein the hydrogen bond is anN—H—N, O—H—O, or N—H—O bond.
 3. The system of claim 1 or 2 comprising atleast 2 of the H-donor molecules and at least 3, preferably at least 4,of the H-acceptor molecules.
 4. The system of any one of claims 1-3wherein the organic or metallo-organic energy and/or charge variablemoieties are semi-conductors.
 5. The system of any one of claims 1-4wherein the organic or metallo-organic energy and/or charge variablemoieties having the lowest energy state is a luminescence dye.
 6. Thesystem of any one of claims 1-5 wherein the H-donor and H-acceptormolecules are soluble in a solvent.
 7. A system for use in an electricor optical device comprising at least two organic or metallo-organicenergy and/or charge variable moieties having conjugated unsaturatedbonds, wherein at least one moiety has an energy state different fromanother of said moieties, characterized in that the system is aH-donor-H-acceptor system comprising at least one H-donor moleculehaving at least two hydrogen bonding clusters, each cluster comprisingat least two groups having formed a hydrogen bond, and at least twoH-acceptor molecules, each having at least one hydrogen bonding cluster,each cluster comprising at least two groups having formed a hydrogenbond with the groups of the H-donor molecule, at least one of theH-donor and H-acceptor molecules further comprising at least an organicor metallo-organic energy and/or charge variable moiety havingconjugated unsaturated bonds, wherein at least one of the H-acceptor andH-donor has formed a complex or is bonded to a backbone having aplurality of hydrogen bonding clusters.
 8. The system of claim 7 whereinthe organic or metallo-organic energy and/or charge variable moietiesare semi-conductors.
 9. An electronic device having at least twoelectrodes with at least one layer of the system of any one of claims1-8 dispersed therein between.
 10. The electronic device of claim 9wherein the device is an electroluminescent device, field-effecttransistor, sensor or photovoltaic device.